FDISK(8)                     System Administration                    FDISK(8)

       fdisk - manipulate disk partition table

       fdisk [options] device

       fdisk -l [device...]

       fdisk  is a dialog-driven program for creation and manipulation of par-
       tition tables.  It understands GPT, MBR, Sun, SGI and BSD partition ta-

       Block devices can be divided into one or more logical disks called par-
       titions.  This division is recorded in  the  partition  table,  usually
       found in sector 0 of the disk.  (In the BSD world one talks about `disk
       slices' and a `disklabel'.)

       All partitioning is driven by device I/O limits (the topology)  by  de-
       fault.   fdisk is able to optimize the disk layout for a 4K-sector size
       and use an alignment offset on modern devices for MBR and GPT.   It  is
       always  a  good  idea  to follow fdisk's defaults as the default values
       (e.g. first and last partition sectors) and partition  sizes  specified
       by  the +/-<size>{M,G,...} notation are always aligned according to the
       device properties.

       CHS (Cylinder-Head-Sector) addressing is deprecated and not used by de-
       fault.   Please,  do  not  follow old articles and recommendations with
       "fdisk -S <n> -H <n>" advices for SSD or 4K-sector devices.

       Note that partx(8) provides a rich interface for scripts to print  disk
       layouts,  fdisk  is mostly designed for humans.  Backward compatibility
       in the output of fdisk is not guaranteed.   The  input  (the  commands)
       should always be backward compatible.

       -b, --sector-size sectorsize
              Specify  the  sector  size  of  the disk.  Valid values are 512,
              1024, 2048, and 4096.  (Recent kernels  know  the  sector  size.
              Use  this option only on old kernels or to override the kernel's
              ideas.)  Since  util-linux-2.17,  fdisk  differentiates  between
              logical and physical sector size.  This option changes both sec-
              tor sizes to sectorsize.

       -B, --protect-boot
              Don't erase the begin of the first disk sector when create a new
              disk label.  This feature is supported for GPT and MBR.

       -c, --compatibility[=mode]
              Specify  the compatibility mode, 'dos' or 'nondos'.  The default
              is non-DOS mode.  For backward compatibility, it is possible  to
              use  the option without the mode argument -- then the default is
              used.  Note that the optional mode argument cannot be  separated
              from  the  -c option by a space, the correct form is for example

       -h, --help
              Display a help text and exit.

       -L, --color[=when]
              Colorize the output.  The optional argument when  can  be  auto,
              never  or  always.  If the when argument is omitted, it defaults
              to auto.  The colors can be disabled; for the  current  built-in
              default see the --help output.  See also the COLORS section.

       -l, --list
              List  the  partition  tables  for the specified devices and then
              exit.  If no devices are given, those mentioned in  /proc/parti-
              tions (if that file exists) are used.

       -o, --output list
              Specify which output columns to print.  Use --help to get a list
              of all supported columns.

              The default list of columns may be extended if list is specified
              in the format +list (e.g. -o +UUID).

       -s, --getsz
              Print  the  size in 512-byte sectors of each given block device.
              This option is DEPRECATED in favour of blockdev(1).

       -t, --type type
              Enable support only for disklabels of the  specified  type,  and
              disable support for all other types.

       -u, --units[=unit]
              When  listing  partition  tables,  show sizes in 'sectors' or in
              'cylinders'.  The default is to  show  sizes  in  sectors.   For
              backward compatibility, it is possible to use the option without
              the unit argument -- then the default is used.   Note  that  the
              optional unit argument cannot be separated from the -u option by
              a space, the correct form is for example '-u=cylinders'.

       -C, --cylinders number
              Specify the number of cylinders of the disk.  I have no idea why
              anybody would want to do so.

       -H, --heads number
              Specify the number of heads of the disk.  (Not the physical num-
              ber, of course, but the number used for partition tables.)  Rea-
              sonable values are 255 and 16.

       -S, --sectors number
              Specify  the  number of sectors per track of the disk.  (Not the
              physical number, of course, but the number  used  for  partition
              tables.) A reasonable value is 63.

       -w, --wipe when
              Wipe  filesystem,  RAID  and partition-table signatures from the
              device, in order to avoid  possible  collisions.   The  argument
              when  can  be  auto,  never  or always.  When this option is not
              given, the default is auto, in which case signatures  are  wiped
              only when in interactive mode.  In all cases detected signatures
              are reported by warning messages before a new partition table is
              created.  See also wipefs(8) command.

       -W, --wipe-partition when
              Wipe  filesystem,  RAID  and  partition-table  signatures from a
              newly created partitions, in order to avoid possible collisions.
              The  argument  when can be auto, never or always.  When this op-
              tion is not given, the default is auto, in which case signatures
              are  wiped  only when in interactive mode and after confirmation
              by user.  In all cases detected signatures are reported by warn-
              ing  messages  before  a  new  partition  is  created.  See also
              wipefs(8) command.

       -V, --version
              Display version information and exit.

       The device is usually /dev/sda, /dev/sdb or so.  A device  name  refers
       to  the entire disk.  Old systems without libata (a library used inside
       the Linux kernel to support ATA host controllers and  devices)  make  a
       difference  between  IDE and SCSI disks.  In such cases the device name
       will be /dev/hd* (IDE) or /dev/sd* (SCSI).

       The partition is a device name followed by a partition number.  For ex-
       ample,  /dev/sda1  is the first partition on the first hard disk in the
       system.  See also Linux  kernel  documentation  (the  Documentation/de-
       vices.txt file).

       The  "last sector" dialog accepts partition size specified by number of
       sectors or by +/-<size>{K,B,M,G,...} notation.

       If the size is prefixed by  '+' then it is interpreted as  relative  to
       the partition first sector.  If the size is prefixed by  '-' then it is
       interpreted as relative to the high limit (last  available  sector  for
       the partition).

       In  the case the size is specified in bytes than the number may be fol-
       lowed by the multiplicative suffixes KiB=1024, MiB=1024*1024, and so on
       for GiB, TiB, PiB, EiB, ZiB and YiB. The "iB" is optional, e.g. "K" has
       the same meaning as "KiB".

       The relative sizes are always aligned according to device  I/O  limits.
       The +/-<size>{K,B,M,G,...} notation is recommended.

       For  backward  compatibility  fdisk  also accepts the suffixes KB=1000,
       MB=1000*1000, and so on for GB, TB, PB, EB, ZB and YB. These 10^N  suf-
       fixes are deprecated.

       fdisk  allows  to read (by 'I' command) sfdisk compatible script files.
       The script is applied to in-memory partition table, and then it is pos-
       sible to modify the partition table before you write it to the device.

       And  vice-versa it is possible to write the current in-memory disk lay-
       out to the script file by command 'O'.

       The script files are compatible between cfdisk, sfdisk, fdisk  and  an-
       other libfdisk applications. For more details see sfdisk(8).

       GPT (GUID Partition Table)
              GPT  is  modern  standard for the layout of the partition table.
              GPT uses 64-bit logical block addresses,  checksums,  UUIDs  and
              names  for partitions and an unlimited number of partitions (al-
              though the number of partitions is usually restricted to 128  in
              many partitioning tools).

              Note  that  the  first sector is still reserved for a protective
              MBR in the GPT specification.  It prevents MBR-only partitioning
              tools from mis-recognizing and overwriting GPT disks.

              GPT  is  always  a  better choice than MBR, especially on modern
              hardware with a UEFI boot loader.

       DOS-type (MBR)
              A DOS-type partition table can describe an unlimited  number  of
              partitions.   In sector 0 there is room for the description of 4
              partitions (called `primary').  One of these may be an  extended
              partition;  this  is  a box holding logical partitions, with de-
              scriptors found in a linked list of sectors, each preceding  the
              corresponding  logical partitions.  The four primary partitions,
              present or not, get numbers 1-4.  Logical  partitions  are  num-
              bered starting from 5.

              In  a  DOS-type partition table the starting offset and the size
              of each partition is stored in two ways: as an  absolute  number
              of  sectors (given in 32 bits), and as a Cylinders/Heads/Sectors
              triple (given in  10+8+6  bits).   The  former  is  OK  --  with
              512-byte  sectors this will work up to 2 TB.  The latter has two
              problems.  First, these C/H/S fields can be filled only when the
              number  of  heads and the number of sectors per track are known.
              And second, even if we know what these numbers should be, the 24
              bits  that  are  available do not suffice.  DOS uses C/H/S only,
              Windows uses both, Linux never uses C/H/S.  The C/H/S addressing
              is  deprecated  and  may be unsupported in some later fdisk ver-

              Please, read the DOS-mode section  if  you  want  DOS-compatible
              partitions.   fdisk  does  not care about cylinder boundaries by

              A BSD/Sun disklabel can describe  8  partitions,  the  third  of
              which should be a `whole disk' partition.  Do not start a parti-
              tion that actually uses its first sector (like a swap partition)
              at cylinder 0, since that will destroy the disklabel.  Note that
              a BSD label is usually nested within a DOS partition.

              An IRIX/SGI disklabel can describe 16 partitions,  the  eleventh
              of which should be an entire `volume' partition, while the ninth
              should be labeled `volume header'.  The volume header will  also
              cover the partition table, i.e., it starts at block zero and ex-
              tends by default over five cylinders.  The  remaining  space  in
              the  volume  header may be used by header directory entries.  No
              partitions may overlap with the  volume  header.   Also  do  not
              change  its  type  or make some filesystem on it, since you will
              lose the partition table.  Use this  type  of  label  only  when
              working  with Linux on IRIX/SGI machines or IRIX/SGI disks under

       A sync() and an ioctl(BLKRRPART) (rereading the  partition  table  from
       disk)  are  performed  before exiting when the partition table has been

DOS mode and DOS 6.x WARNING
       Note that all this is deprecated. You don't have to care  about  things
       like  geometry and cylinders on modern operating systems. If you really
       want DOS-compatible partitioning then you have to enable DOS  mode  and
       cylinder  units  by  using the '-c=dos -u=cylinders' fdisk command-line

       The DOS 6.x FORMAT command looks for some information in the first sec-
       tor  of  the data area of the partition, and treats this information as
       more reliable than the information in the partition table.  DOS  FORMAT
       expects  DOS  FDISK  to clear the first 512 bytes of the data area of a
       partition whenever a size change occurs.  DOS FORMAT will look at  this
       extra  information  even  if the /U flag is given -- we consider this a
       bug in DOS FORMAT and DOS FDISK.

       The bottom line is that if you use fdisk or cfdisk to change  the  size
       of  a  DOS  partition table entry, then you must also use dd(1) to zero
       the first 512 bytes of that partition before using DOS FORMAT to format
       the partition.  For example, if you were using fdisk to make a DOS par-
       tition table entry for /dev/sda1, then (after exiting fdisk and reboot-
       ing  Linux  so that the partition table information is valid) you would
       use the command "dd if=/dev/zero of=/dev/sda1 bs=512 count=1"  to  zero
       the first 512 bytes of the partition.

       fdisk  usually  obtains  the  disk geometry automatically.  This is not
       necessarily the physical disk geometry (indeed, modern disks do not re-
       ally  have  anything  like a physical geometry, certainly not something
       that can be described in the simplistic Cylinders/Heads/Sectors  form),
       but it is the disk geometry that MS-DOS uses for the partition table.

       Usually all goes well by default, and there are no problems if Linux is
       the only system on the disk.  However, if the disk  has  to  be  shared
       with  other  operating systems, it is often a good idea to let an fdisk
       from another operating system make at least one partition.  When  Linux
       boots  it looks at the partition table, and tries to deduce what (fake)
       geometry is required for good cooperation with other systems.

       Whenever a partition table is printed out in DOS  mode,  a  consistency
       check is performed on the partition table entries.  This check verifies
       that the physical and logical start and end points are  identical,  and
       that  each partition starts and ends on a cylinder boundary (except for
       the first partition).

       Some versions of MS-DOS create a first partition which does  not  begin
       on  a cylinder boundary, but on sector 2 of the first cylinder.  Parti-
       tions beginning in cylinder 1 cannot begin on a cylinder boundary,  but
       this  is  unlikely to cause difficulty unless you have OS/2 on your ma-

       For best results, you should always use an OS-specific partition  table
       program.   For  example,  you  should  make DOS partitions with the DOS
       FDISK program and Linux partitions with the Linux fdisk or Linux cfdisk

       Implicit  coloring  can be disabled by an empty file /etc/terminal-col-

       See terminal-colors.d(5) for more details about colorization configura-
       tion. The logical color names supported by fdisk are:

       header The header of the output tables.

              The help section titles.

       warn   The warning messages.

              The welcome message.

       Karel Zak <kzak@redhat.com>
       Davidlohr Bueso <dave@gnu.org>

       The  original version was written by Andries E. Brouwer, A. V. Le Blanc
       and others.

              enables fdisk debug output.

              enables libfdisk debug output.

              enables libblkid debug output.

              enables libsmartcols debug output.

              use  visible  padding  characters.  Requires  enabled  LIBSMART-

       cfdisk(8), mkfs(8), partx(8), sfdisk(8)

       The  fdisk  command  is part of the util-linux package and is available
       from https://www.kernel.org/pub/linux/utils/util-linux/.

util-linux                       February 2016                        FDISK(8)
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